The drive mechanism for conventional incline conveyors generally involve drive pulleys and idler rollers in various configurations. Incline conveyors are commonly arranged such that the belt passes over two cylindrical rollers, one at the input (tail) end and the other at the output (head) end of the conveyor. Friction between the contact surface area of one or more powered drive rollers and the conveyor belt causes the endless belt to be driven.
A single-end drive pulley is commonly used to drive incline conveyors. Typically, the input roller is an idler roller; and the output roller is driven by a motor, and referred as the drive roller. Alternatively, the input roller could be driven and the output roller could be an idler. An example of an end drive conveyor is shown in U.S. Pat. No. 6,675,958 “Tube Conveyor” to Kaeb et al, the disclosure of which is incorporated by reference, which describes an endless belt incline conveyor driven from the input end or the output end.
Alternatively, an incline conveyor can have idler rollers at both the input and output ends and be driven by an S-drive roller mechanism located between the ends. An example of a center S-drive conveyor is shown in U.S. Pat. No. 5,452,791 “Dual Drive for Belt Conveyor” to Morency et al, which describes an endless belt conveyor driven by center positioned tandem drive rollers. The two driving rollers engage the belt in an S-shaped drive roller configuration. Other similar configurations utilize a single driven roller and a snub roller that properly positions the belt around the drive roller.
Proper conveyor belt tensioning is necessary to transfer power from the drive roller to the conveyor belt. Semi-elastic conveyor belts are generally installed around the end rollers, cut to length, and the belt ends are spliced together to form an endless conveyor belt. One or more end idler rollers are adjusted to stretch the semi-elastic conveyor belt around the end rollers. Generally, only the idler roller is adjustable since the drive roller is attached to the power source. For example, when the drive roller is moved, the power source must also be moved in order to maintain proper alignment of the power source components such as v-belts, gearboxes, and motors. Alternatively, snub rollers and S-shape roller configurations are used to apply tension to the conveyor belt.
However, certain types of substantially uneven conveyor belts, such as the cleated belt described in U.S. Pat. No. 6,170,646 to Kaeb et al, “Cleated Belt Adaptable to Curvilinear Shapes”, the disclosure of which is incorporated by reference, interfere with rollers that contact the carrying surface of the cleated belt. As such, uneven conveyor belts cannot utilize snub rollers or drive rollers in an S-shape configuration for driving the belt or for tensioning.
As a result, incline conveyors with substantially uneven belts are generally powered by a single drive roller in the head or tail of the conveyor. These conveyors have limited drive roller surface area, which limits the amount of driving energy that can be transferred to the conveyor belt through friction between the roller and the belt. Therefore the length and capacity of the conveyor is limited. One solution is to increase the diameter of the drive roller, thus increasing the contact surface area. However, the use of larger diameter drive rollers requires the use of many other enlarged conveyor components, which leads to increases in the size, weight, and cost of the conveyor.
Longer conveyors also require greater conveyor belt uptake tensioning distances. Tensioning an uneven conveyor belt, such as a cleated belt, is generally accomplished by adjusting the position of the end idler roller relative to the end drive roller. The distance the end roller must be adjusted to maintain tension increases with conveyor length. Tensioning bolts are utilized on either side of the end idler roller to stretch the semi-elastic conveyor belt to the predetermined degree of tension.
Therefore it is apparent that there are numerous challenges in to using existing solutions to drive and tension a long, high capacity conveyor with a substantially uneven conveyor belt surface. Another limitation is the inability to properly tension the conveyor belt using adjustable end rollers when the end roller is driven, when the end roller is a driven roller that needs to maintain proper tension with a gear box through a drive belt. Existing solutions to drive and tension long conveyor belts rely on multiple independent power sources to drive the input and the output drive rollers.